Conventional computer networks are susceptible to attacks from malicious transmissions such as viruses, worms, and Trojan horses. Such malicious transmissions infiltrate a user computer system and perform an undesirable operation, such as deleting files, consuming excessive resources, or causing other undesired operation. A common trait of many conventional viruses is to replicate the virus itself to other computer systems in communication with the already infected computer system. Often, just as with biological viruses, a computer virus operates as a dormant carrier, “infecting,” or replicating itself to other computer systems without manifesting symptoms on the carrier host. In this manner, a virus is likely to infect many more systems prior to detection and elimination than if the virus was readily apparent to a user.
Conventional viruses often employ email as a propagation vehicle for replication. Conventional email provides a widely available and installed base of software for transmitting and receiving to other computer systems. Often, email also provides a seamless way to execute components of the email as live code. Such conventional email systems employ attachments as a convenient method of incorporating distinct components of varying types into the conventional email message. Accordingly, an unsuspecting user operating with an unprotected email system provides an easy target for such a malicious transmission